With its magnificently tranquil art gallery, its ‘lonely library’ and its pointy white chapel, Aranya is a blissful oasis for burnt-out urbanites – and architecture firms are now clambering to build there

Every summer, since the days of Mao Zedong, the leaders of China’s Communist party have decamped to the coastal resort of Beidaihe to debate the country’s future from the comfort of luxurious seaside villas hidden behind high walls. Four hours’ drive from the distractions of Beijing, it has been a perfect place to escape the capital’s stifling heat, take in the sea air, and conduct secretive conclaves in heavily guarded compounds, in between refreshing dips.

But in recent years, the region has been attracting visitors of a very different kind. On a chilly morning, just a little way south along the coast, the windswept beach is teaming with style-conscious twentysomethings. Crowds of young tourists, wrapped in thick down coats, queue up to take photos in sub-zero temperatures – not next to statues of Mao, but in front of striking works of contemporary architecture.

Has architecture taken over the bloom bonanza? Our critic finds an elfin treehouse, a pixie grotto, a Roman villa and a £160,000 shepherd’s hut (with spa) now competing with the delphiniums

A gigantic Chinese dragon made of gnarled chunks of driftwood towers over a display of bog plants, puffing steam from its nostrils and clutching a ceramic pearl that gushes with water. Nearby, men dressed in togas patrol the courtyard of a pretend Roman villa, where simulated rain pours into the garden from a pantiled roof. Around the corner, a waterfall cascades down an artificial rock face, creating an arresting backdrop to a display of luxury outdoor sofa cushions.

Welcome to the RHS Chelsea flower show, a surreal phenomenon that has gone from an annual fair of prized blooms to a multimillion-pound Disneyfied spectacular, where the flowers now struggle to hold their own against ever more elaborate pieces of set design.

Every year, in the space of just three weeks, the grounds of Christopher Wren’s Royal hospital in London are transformed into an unrecognisable wonderland of horticultural fantasies. It is a place where elfin treehouses compete for attention with pixie grottos, and sculpted clay stupas loom above moss-encrusted ruins. It feels like wandering around a themed food court, with Moroccan tiled courtyards jostling with Japanese bridges, thatched Burmese stilt houses vying with Welsh dry-stone walls. The cuisine on offer might not be as international, but you can wash down the global garden safari with a £15 Pimm’s.

Begun in 1913, in a modest marquee, the Chelsea flower show has mushroomed into a town-sized endeavour. It has become a festival of terraforming as much as flowers, seeing more than 2,000 tonnes of soil moved around the 11-acre site each year, and hundreds more tonnes of rocks, concrete, trees and scenery trucked in from miles around – all for just five days of floricultural theatre. Now, for the first time, this year there is a “green medal” for the garden with the lowest carbon footprint, which feels a bit like holding an exhibition of bonfires, then awarding a prize to the one that produces the least smoke.

A mega egg in Paris, a hovering hotel in Machu Picchu, an hourglass tower in New York, a pleasure island in Baghdad … we reveal the architectural visions that were just too costly – or too weird

Did you know that, if things had gone differently, the Pompidou Centre could have been an egg? In the 1969 competition for the Paris art centre – ultimately won by Richard Rogers and Renzo Piano, with their inside-out symphony of pipework – a radical French architect called André Bruyère submitted a proposal for a gigantic ovoid tower. His bulbous building would have risen 100 metres above the city’s streets, clad in shimmering scales of alabaster, glass and concrete, its walls swelling out in a curvaceous riposte to the tyranny of the straight line.

“Time,” Bruyère declared, “instead of being linear, like the straight streets and vertical skyscrapers, will become oval, in tune with the egg.” His hallowed Oeuf would be held aloft on three chunky legs, while a monorail would pierce the facade and circle through the structure along a sinuous floating ribbon. The atrium was to take the form of an enclosed globe, like a yolk.